1. Technical Field
This invention relates to the manufacturing and assembly of movable sockets, for example, ball-joints as used in automotive steering and suspension systems, and more particularly, to a method and device for performing the operation of closing one end of a movable socket by deforming a solid cover-plate and then spinning or swaging a perimeter lip of the housing to retain the deformed cover-plate. While the invention is described in detail with respect to automotive applications, those skilled in the art will recognize the broader applicability of the invention.
2. Related Art
Conventional ball-joints, and other movable sockets are used, for example, in automotive steering and suspension applications. The sockets typically comprise a housing having a circular cylindrical internal surface, a ball stud with a ball head contained in the housing, and a bearing member supporting the ball head within the housing. These components are typically installed into the housing through a posterior opening, with the ball stud extending outward through an axially disposed anterior opening of a smaller diameter than the ball head. Traditionally, the posterior opening is closed by means of a flat cover-plate, which is spun or swaged in place. Alternatively, the cover-plate may be welded into place. In such sockets the control of the preload of the socket components through pressure applied by the cover-plate in conjunction with closure of the socket is very important to the proper function of the socket in its intended application.
Cover-plate elements are traditionally formed from a stamping process, whereby individual components having desired dimensions are stamped from metal sheets. Either during the stamping process or in a subsequent manufacturing step, a raised boss may be drawn or stamped into the cover-plate, and a centrally located hole of predetermined dimensions punched therein to receive a self-tapping or threaded grease fitting. Once secured in place, the cover-plate presses on the bearing member either directly, or indirectly through a resilient intermediate component and a pressure plate or bearing member.
Once assembled, movable sockets may be utilized as position controlling, load carrying members in numerous mechanical systems, including automotive vehicle suspension and steering systems. Obviously, movable sockets or ball-joints employed in these applications are subjected to various operating conditions, and may be required to carry substantial loads. When wear develops, the performance of the movable socket or ball-joint degrades and, in the case of automotive applications, may result in erratic steering or excessive looseness and play in the vehicle suspension system.
As described in U.S. Pat. No. 6,202,280 B1, herein incorporated by reference, a method and device for expanding a conical or convex cover-plate within a circumferential groove in the posterior opening may be employed to secure and enclose the socket components within the socket housing, allowing for closure of a fully hardened housing without the need for additional steps to close the socket and secure the cover-plate.
Alternately, as is described in U.S. Pat. No. 6,125,541 to Parker, herein incorporated by reference, a two-stage ram having first and second contact surfaces may be utilized to first expand a conical or convex wear-indicator style cover-plate, having an axial opening, within the circumferential groove in the posterior opening of a housing, and then to further deform the cover-plate to a predetermined final position relative to the internal components of the socket to provide a predetermined wear indicator distance.
Similarly, as is described in U.S. Pat. No. 6,532,665 B2 to Parker, herein incorporated by reference, a two-stage ram having a contact surface and a concentric pivot punch may be brought into engagement with the cover-plate within the posterior opening of a housing for the purpose of closing the housing. Pressure exerted by the two-stage ram is transferred to the cover-plate through the contact surface, expanding the cover-plate to conform to the contact surface and enclosing the internal components of the socket within the socket housing. The exerted pressure additionally results in the extension of the concentric pivot punch into the central orifice of the cover-plate, thereby controlling the expansion of the cover-plate and establishing the central orifice to predetermined dimensions upon closure of the socket housing.
Each of the aforementioned sockets and apparatuses and methods for closing a movable socket with a ram requires that the cover-plate incorporate an axial opening to permit the desired deformation under load from the ram. However, some socket designs require a sealed or closed cover-plate having no axial opening. In many such applications, the socket is lubricated only prior to the assembly process, and is not lubricated after assembly. These are often referred to as “lubed for life” sockets. U.S. Pat. No. 6,619,873 B2 to Parker, herein incorporated by reference, sets forth and describes an assembly technique for expanding a sealed or closed cover plate having no axial opening into the open end of a socket housing, thereby closing the socket.
The socket housing designs set forth above and utilized with deformable or expanding cover-plates have limited socket wall thickness due to the design of the cover-plate step and the need to incorporate a fully-formed circumferential groove on the inner surface of the housing opening, adjacent the cover-plate step. Accordingly, it would be advantageous to provide a housing which does not require a reduction in wall thickness due to incorporation of a circumferential groove for capturing the cover-plate. Further, it would also be advantageous to provide a housing which can be utilized with deformable cover-plates, and which retains the low-profile top surface benefits of conventional spun or swaged housings, providing clearance for surrounding components after installation of the socket in a corresponding application. Still further, it would be advantageous to provide a socket housing with ductility sufficient to permit deformation of the top surface of the housing and the use of housing designs which have a low-profile top surface.